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Effects of Gluten Intake on Risk of Celiac Disease: A Case-Control Study on a Swedish Birth Cohort

Published:October 07, 2015DOI:https://doi.org/10.1016/j.cgh.2015.09.030

      Background & Aims

      Early nutrition may affect the risk of celiac disease. We investigated whether amount of gluten in diet until 2 years of age increases risk for celiac disease.

      Methods

      We performed a 1-to-3 nested case-control study of 146 cases, resulting in 436 case-control pairs matched for sex, birth year, and HLA genotype generated from Swedish children at genetic risk for celiac disease. Newborns were annually screened for tissue transglutaminase autoantibodies (tTGA). If tested tTGA positive, time point of seroconversion was determined from frozen serum samples taken every 3 months. Celiac disease was confirmed by intestinal biopsies. Gluten intake was calculated from 3-day food records collected at ages 9, 12, 18 and 24 months. Odds ratios (OR) were calculated through conditional logistic regression.

      Results

      Breastfeeding duration (median, 32 wk) and age at first introduction to gluten (median, 22 wk) did not differ between cases and tTGA-negative controls. At the visit before tTGA seroconversion, cases reported a larger intake of gluten than controls (OR, 1.28; 95% confidence interval [CI], 1.13–1.46; P = .0002). More cases than controls were found in the upper third tertile (ie, >5.0 g/d) before they tested positive for tTGA seroconversion than controls (OR, 2.65; 95% CI, 1.70–4.13; P < .0001). This finding was similar in children homozygous for DR3-DQ2 (OR, 3.19; 95% CI, 1.61–6.30; P = .001), heterozygous for DR3-DQ2 (OR, 2.24; 95% CI, 1.08-4.62; P = .030), and for children not carrying DR3-DQ2 (OR, 2.43; 95% CI, 0.90–6.54; P = .079).

      Conclusions

      The amount of gluten consumed until 2 years of age increases the risk of celiac disease at least 2-fold in genetically susceptible children. These findings may be taken into account for future infant feeding recommendations.

      Keywords

      Abbreviations used in this paper:

      CD (celiac disease), TEDDY (The Environmental Determinants of Diabetes in the Young), tTGA (tissue transglutaminase autoantibodies)
      See editorial on page 410.
      Celiac disease (CD) is an emerging public health disorder affecting 1% to 3% of the general population, with variations between ethnic groups and geographic regions.
      • Ludvigsson J.F.
      • Green P.H.
      Clinical management of coeliac disease.
      Both gluten exposure and carrying any of the HLA-risk haplotypes DR3-DQ2 and DR4-DQ8 are necessities for the risk of CD.
      • Catassi C.
      • Gatti S.
      • Fasano A.
      The new epidemiology of celiac disease.
      • Sollid L.M.
      • Thorsby E.
      HLA susceptibility genes in celiac disease: genetic mapping and role in pathogenesis.
      However, gluten is a universally consumed food antigen and half of the Caucasian population possesses at least 1 of these 2 risk haplotypes,
      • Hunt K.A.
      • Zhernakova A.
      • Turner G.
      • et al.
      Newly identified genetic risk variants for celiac disease related to the immune response.
      suggesting that additional environmental factors determine whether lifelong gluten intolerance develops in an individual at genetic risk.
      Age at first introduction to gluten or the risk of CD has long been debated. Retrospective data generated in Sweden have indicated that introducing gluten in small amounts between 4 and 6 months of age while being breastfed reduces the risk of celiac disease compared with introducing gluten in larger amounts at older ages.
      • Ivarsson A.
      • Persson L.A.
      • Nyström L.
      • et al.
      Epidemic of coeliac disease in Swedish children.
      • Ivarsson A.
      • Myléus A.
      • Norström F.
      • et al.
      Prevalence of childhood celiac disease and changes in infant feeding.
      The hypothesis of an optimal time window for inducing tolerance to gluten recently was questioned by results of prospective cohort studies.
      • Stördal K.
      • White R.A.
      • Eggesbö M.
      Early feeding and risk of celiac disease in a prospective birth cohort.
      • Aronsson C.A.
      • Lee H.
      • Liu E.
      • et al.
      Age at gluten introduction and risk for celiac disease.
      Furthermore, 2 recent randomized controlled intervention studies failed to show an effect of timing of gluten introduction on risk of CD, and neither study directly examined the impact of the quantity of gluten intake.
      • Vriezinga S.M.
      • Auricchio R.
      • Bravi E.
      • et al.
      Randomized feeding intervention in infants at high risk for celiac disease.
      • Lionetti E.
      • Castellaneta S.
      • Francavilla R.
      • et al.
      Introduction of gluten, HLA status and the risk of celiac disease in children.
      Although retrospective data from Sweden pointed to the importance of quantity of gluten intake for risk of CD,
      • Ivarsson A.
      • Hernell O.
      • Stenlund H.
      • et al.
      Breast-feeding protects against celiac disease.
      no prospective studies free of recall bias have been performed to date.
      The Environmental Determinants of Diabetes in the Young (TEDDY) study is an international prospective birth cohort study following up genetically susceptible children in search of environmental factors associated with type 1 diabetes and CD.
      TEDDY Study group
      The Environmental determinants of Diabetes in The Young (TEDDY) study: study design.
      TEDDY has previously confirmed that the risk for celiac disease by 5 years of age is dependent on HLA genotype, and that children with the highest-risk group (ie, homozygous for DR3/DQ2) develop CD-associated autoantibodies to tissue transglutaminase (tTGA) much earlier compared with children carrying a single or no DR3-DQ2 haplotype.
      • Liu E.
      • Lee H.
      • Aronsson C.A.
      • et al.
      HLA Haplotype and country and the risk of celiac disease in early childhood.
      In addition, Swedish TEDDY participants are at the highest risk for CD at an early age compared with participants in other TEDDY countries.
      • Liu E.
      • Lee H.
      • Aronsson C.A.
      • et al.
      HLA Haplotype and country and the risk of celiac disease in early childhood.
      Swedish infants traditionally receive gluten-containing follow-up formulas and porridge during the first 2 years of life.
      • Weile B.
      • Cavell B.
      • Nivenius K.
      • et al.
      Striking differences in the incidence of childhood celiac disease between Denmark and Sweden: a plausible explanation.
      Although Swedish TEDDY participants are introduced to gluten earlier than children in the other countries, the age at which gluten was introduced did not explain why Swedish children were at increased risk for CD in the TEDDY study.
      • Aronsson C.A.
      • Lee H.
      • Liu E.
      • et al.
      Age at gluten introduction and risk for celiac disease.
      In this study, we investigated if the amount of gluten intake during the first 2 years of life is a risk factor for CD.

      Patients and Methods

       Study Population

      The TEDDY study was conducted in 6 clinical centers in Finland, Germany, Sweden, and the United States, and was approved by local Institutional Review Boards and monitored by an External Advisory Board formed by the National Institutes of Health.
      TEDDY Study group
      The Environmental Determinants of Diabetes in The Young (TEDDY) study.
      Between September 2004 and February 2010, a total of 424,788 newborns were HLA genotyped at 1 of these 6 sites and were eligible if they had one of the following HLA genotypes: DR3-DQ2/DR4-DQ8, DR4-DQ8/DR4-DQ8, DR4-DQ8/DR8, DR3-DQ2/DR3-DQ2, DR4-DQ8/DR4b, DR4-DQ8/DR1, DR4-DQ8/DR13, DR4-DQ8/DR9, or DR3-DQ2/DR9.
      • Hagopian W.A.
      • Erlich H.
      • Lernmark Å.
      • et al.
      The Environmental Determinants of Diabetes in The Young (TEDDY): genetic criteria and international diabetes risk screening of 410 000 infants.
      Of the screened newborns, 48,140 were from the Swedish site, of whom 3723 (7.7%) were HLA-eligible and invited to participate in a 15-year follow-up period. Written informed consent was obtained from parents or primary caretakers in 2525 of the 3723 (68%).
      • Hagopian W.A.
      • Erlich H.
      • Lernmark Å.
      • et al.
      The Environmental Determinants of Diabetes in The Young (TEDDY): genetic criteria and international diabetes risk screening of 410 000 infants.
      Annual screening for CD starts from the age of 2 years with tTGA using radiobinding assays as described elsewhere.
      • Vehik K.
      • Fiske S.W.
      • Logan C.D.
      • et al.
      Methods, quality control and specimen management in an international multi-center investigation of type 1 diabetes: TEDDY.
      Earlier blood samples collected from birth and onward were analyzed retrospectively to determine the age of seroconversion in cases with tTGA positivity.
      • Liu E.
      • Lee H.
      • Aronsson C.A.
      • et al.
      HLA Haplotype and country and the risk of celiac disease in early childhood.
      Children who tested positive for tTGA in 2 consecutive samples were defined as persistently tTGA positive and referred to their health care provider for evaluation of CD with an intestinal biopsy. A biopsy showing a Marsh score of 2 or greater in tTGA-positive children proved CD.
      • Liu E.
      • Lee H.
      • Aronsson C.A.
      • et al.
      HLA Haplotype and country and the risk of celiac disease in early childhood.
      At time of this study, 2062 of the Swedish children had been screened for tTGA, of whom 330 were persistently tTGA positive and 147 were diagnosed with CD (Supplementary Figure 1).

       Study Design

      A 1-to-3 matched nested case-control study was conducted on Swedish children screened for tTGA. Cases were defined as children with biopsy-confirmed CD. All controls were tTGA negative within 45 days of the case's age of seroconversion of tTGA and free of biopsy-confirmed CD within 45 days of the cases age at biopsy. Age at seroconversion of tTGA was set as the age when the first positive sample was drawn. Sex and HLA genotype (ie, the number of DR3-DQ2 alleles) were chosen as matching factors.
      • Liu E.
      • Lee H.
      • Aronsson C.A.
      • et al.
      HLA Haplotype and country and the risk of celiac disease in early childhood.
      Controls also were matched to the cases for birth year to control for changes in nutrient and food composition in commercial baby foods available on the Swedish market during the follow-up period. Three controls per case were selected randomly from subjects who met these matching criteria. Among the 147 children who were diagnosed with CD, 1 child did not have any eligible controls and another child had only 1 eligible control. In all, the analysis included 436 case-control pairs from 146 cases. Six cases (4%) and 13 (3%) controls had a first-degree relative with CD. The median age of seroconversion to tTGA was 24 months (range, 10–86 mo), and the median age at diagnosis was 38 months (range, 15–102 mo).

       Dietary Assessment

      Information about breastfeeding duration (exclusive and total breastfeeding) and timing of introduction of gluten-containing cereals were collected every 3 months through a booklet given to the parents at study entry, which has been described in detail elsewhere.
      • Aronsson C.A.
      • Lee H.
      • Liu E.
      • et al.
      Age at gluten introduction and risk for celiac disease.
      Data on overall food consumption were collected by a 24-hour recall at the first clinic visit (age, 3–4.5 mo) and by 3-day food records at clinic visits at 6, 9, 12, 18, and 24 months of age.
      • Yang J.
      • Lynch K.F.
      • Uusitalo U.
      • et al.
      Factors associated with longitudinal food record compliance in a paediatric cohort study.
      Parents were asked to keep a food record covering all foods and drinks consumed by the child for the given 3 days (ideally, 2 weekdays and 1 weekend day) before the scheduled visit. Parents were given instructions on how to fill out the records by trained study personnel. They were advised not to change the eating habits of the child during the time they were completing the food record. Written instructions and guidance were provided to the families. If the primary caregiver indicated that the child had started attending daycare, separate food records were provided for the daycare personnel to complete. At each clinical visit, the food records were reviewed by a study nurse. Probing about missing or unclear information was obtained by face-to-face interview during the visit. Brand names were requested for all commercial baby foods. Portion sizes were estimated using household measures, drawings, and pictures from a booklet. Each set of photographs of foods and dishes contained 4 to 5 portion sizes in increasing order. Drawings and shapes of other types of foods such as bread, cakes, and pizza also were included. For soft bread, drawings of actual size of bread slices and thicknesses were provided. The booklet was handed out to the families at study entry and used at home when keeping the food records.
      Gluten-containing foods included products and composite dishes (such as pizza and sandwiches) with wheat, rye, and barley, but not oats. Oats consists of proteins that will not lead to the same intestinal damage as wheat, rye, and barley, and therefore were treated as a non–gluten-containing cereal.
      • Koskinen O.
      • Villanen M.
      • Korponay-Szabo I.
      • et al.
      Oats do not induce systemic or mucosal autoantibody response in children with coeliac disease.
      The food database and connected software enables the summarization of intake of each food and food group.
      • Uusitalo U.
      • Kronberg-Kippilä C.
      • Andren Aronsson C.
      • et al.
      Food composition database harmonization for between-country comparisons of nutrient data in the TEDDY study.
      Recipes were created to describe ingredients in dishes. For commercial baby foods containing gluten, specific recipes were created for each brand name based on the ingredient list. The Swedish National Food Composition Database was used as a source for nutrient content and standard recipes of foods such as bread, sweet bakery, pancakes, pizza, and so forth.

      National Food Agency, Uppsala, Sweden. The Swedish Food Composition Database. Available: http://www.slv.se/en-gb/Group1/Food-and-Nutrition/The-Food-Database/. Assessed: November 20, 2014.

      Unique user recipes provided by the parents were added and used in the local database. All recipes were broken down to ingredients, and intake of gluten-containing flours was summarized and the mean intake of the 3-day recording period was calculated as grams per day. The daily gluten intake was calculated from the amount of vegetable protein in gluten-containing flours and then multiplied by a factor of 0.8.
      • van Overbeek F.M.
      • Uil-Dieterman I.G.
      • Mol I.W.
      • et al.
      The daily gluten intake in relatives of patients with coeliac disease compared with that of the general Dutch population.
      At the age of 6 months, 97% of the children’s families had submitted complete food records, and 84% of the food records were submitted at the age of 24 months.

       Statistical Analyses

      The Kruskal–Wallis test was used to compare the age of tTGA seroconversion in the cases by sex, birth year, and HLA. Conditional logistic regression was used to compare characteristics in cases with those in matched controls. Gluten intake was estimated from the 3-day food records at the visit before the cases seroconverted to tTGA. The estimate at the visit before the tTGA seroconversion was analyzed, as well as total intake, which was defined as the sum of the estimates from all visits up to the visit before the tTGA seroconversion. For cases whose age of seroconversion was older than 24 months, the visit at 24 months of age was used as the visit before seroconversion. The estimated amount of gluten intake at the visit before the tTGA seroconversion was analyzed both as a continuous variable (g/d) and as a trichotomous variable based on tertiles of quantity (ie, low [<3.4 g/d], medium [3.4–5.0 g/d], and high [>5.0 g/d]). The Kaplan–Meier estimates of time to tTGA seroconversion for cases, stratified by tertile of amount of gluten intake, were plotted. For controls currently negative for tTGA, the censored time was the age at collection of the last sample negative for tTGA. For controls currently positive for tTGA, the censored time was the age at collection of the initial sample positive for tTGA. All statistical analyses were performed using SAS, version 9.4 (SAS Institute, Inc, Cary, NC). All reported P values were 2-sided without multiple testing correction, and P values less than .05 were considered to represent statistical significance.

      Results

      Age at first introduction to gluten, breastfeeding duration, or having a first-degree relative with CD were considered as potential confounders, but none of the variables had an impact on the results and therefore were not included in the final analysis. Matching factors and age of seroconversion are described in Table 1.
      Table 1Matching Factors and Age of tTGA Seroconversion in the TEDDY Swedish Birth Cohort and in Children With Celiac Disease
      Matching factorBirth cohort (N = 2062)

      N (%)
      Celiac disease (N = 146)

      N (%)
      Age of tTGA seroconversion

      Median, mo (Q1, Q3)
      P value
      Kruskal–Wallis test P value.
      Sex
       Boys1055 (51)49 (34)29 (21, 48).066
       Girls1007 (49)97 (66)24 (18, 36)
      Birth year
       200491 (4)8 (6)
       2005366 (18)37 (25)28 (18, 48).066
      2004 and 2010 were not included because of the small number of observations.
       2006377 (18)22 (15)30 (21, 59)
       2007412 (20)31 (21)24 (20, 37)
       2008363 (18)25 (17)30 (22, 36)
       2009385 (19)19 (13)21 (17, 24)
       201068 (3)4 (3)
      HLA genotype
       DR3-DQ2/DR3-DQ2438 (21)70 (48)21.5 (17, 28)<.0001
       DR3-DQ2/DR4-DQ8868 (42)48 (33)36 (22.5, 48.5)
      Including DR3-DQ2/DR4-DQ8 and DR3-DQ2/DR9.
       DR3-DQ2/DR91 (<1)
       DR4-DQ8/DR4-DQ8455 (22)26 (18)35 (21.5, 37)
      Including DR4-DQ8/DR4-DQ8, DR4-DQ8/DR8, DR4-DQ8/DR1, DR4-DQ8/DR13, and DR4-DQ8/DR9.
       DR4-DQ8/DR8268 (13)2 (1)
       DR4-DQ8/DR118 (1)
       DR4-DQ8/DR1313 (<1)
       DR4-DQ8/DR91 (<1)
      a Kruskal–Wallis test P value.
      b 2004 and 2010 were not included because of the small number of observations.
      c Including DR3-DQ2/DR4-DQ8 and DR3-DQ2/DR9.
      d Including DR4-DQ8/DR4-DQ8, DR4-DQ8/DR8, DR4-DQ8/DR1, DR4-DQ8/DR13, and DR4-DQ8/DR9.

       Gluten Intake in Cases and Controls

      Total and exclusive breastfeeding duration and age at first introduction to gluten-containing cereals (wheat, rye, or barley) did not differ between cases and controls (Table 2). Cases reported a higher gluten intake than the matched controls (Table 3). If cases and controls with a first-degree relative with CD were excluded, the results were in the same direction (data not shown).
      Table 2Infant Feeding Characteristics in Children With Celiac Disease and Matched Controls
      CharacteristicCeliac disease (N = 146)

      Median (Q1, Q3)
      Controls (N = 436)

      Median (Q1, Q3)
      OR (95% CI)P value
      Breastfeeding duration, wk
       Total31 (20, 40)33 (18, 43)0.99 (0.99–1.00).361
       Exclusive4 (1, 14)6 (1, 16)0.98 (0.96–1.00).124
      Age at first introduction, wk
       Gluten-containing cereals
      Gluten-containing cereals (wheat, rye, or barley).
      22 (18, 24)22 (18, 24)0.99 (0.95–1.04).866
       Wheat22 (20, 25)22 (18, 25)1.00 (0.96–1.05).888
      Energy intake, kcal
      Total energy intake (kcal) at the visit before the cases first positive tTGA test.
      1019 (840, 1164)1009 (858, 1156)1.00 (1.00–1.00).450
      a Gluten-containing cereals (wheat, rye, or barley).
      b Total energy intake (kcal) at the visit before the cases first positive tTGA test.
      Table 3Daily Gluten Intake in Children With Celiac Disease and Matched Controls
      Gluten intakeCeliac disease (N = 146)

      Median (Q1, Q3)
      Controls (N = 436)

      Median (Q1, Q3)
      OR (95% CI)P value
      Total gluten (g) intake before tTGA seroconversion
      Intake from all visits (sum of all visits) up to the visit before the cases first positive tTGA test.
      10.5 (7.6, 14.2)9.9 (5.9, 13.8)1.05 (1.01–1.10).030
      Gluten (g) intake at the visit before tTGA seroconversion4.9 (3.5, 5.9)3.9 (2.9, 5.2)1.28 (1.13–1.46).0002
      a Intake from all visits (sum of all visits) up to the visit before the cases first positive tTGA test.
      One unit (g/d) increase of gluten before seroconversion of tTGA was associated with a 28% increase in risk of CD (P = .0002). Because 14 cases were missing gluten intake data at the visit before seroconversion (2 cases at the 18-month visit and 12 cases at the 24-month visit), 385 pairs from 132 cases were analyzed for the gluten intake before seroconversion of tTGA (Table 4). Gluten intake reported by cases was higher at all ages beginning at 12 months, continuing with a trend toward higher intake at 18 months, and again significantly higher intake was seen at the age of 24 months. Moreover, children who received amounts of gluten in the upper tertile (ie, high gluten intake) were at more than a 2-fold higher risk for CD than those who consumed less (OR, 2.65; 95% CI, 1.70–4.13; P < .0001). Figure 1 shows the Kaplan–Meier plot by 3 groups categorized by tertiles (low, medium, high intake).
      Table 4Daily Gluten Intake at the Clinical Visit Before tTGA Seroconversion in Children With Celiac Disease and Matched Controls
      Age at 3-day food record, moCeliac disease (N = 132)
      Children with data missing at the clinic visit before tTGA seroconversion were excluded (N = 14).
      Controls (N = 385)OR (95% CI)P value
      N
      Children with data missing at the clinic visit before tTGA seroconversion were excluded (N = 14).
      Median, g/d
      Reported gluten intake before age of tTGA seroconversion in children.
      (Q1, Q3)
      NMedian, g/d
      Reported gluten intake before age of tTGA seroconversion in children.
      (Q1, Q3)
      961.6 (1.4, 1.8)171.9 (1.1, 2.4)0.63 (0.19–2.05).444
      12324.9 (3.5, 5.6)893.2 (2.5, 4.5)1.58 (1.17–2.13).003
      18374.9 (3.9, 5.9)1033.9 (3.2, 5.2)1.22 (0.99–1.51).077
      24575.1 (3.7, 6.2)1764.3 (3.3, 5.7)1.23 (1.01–1.49).043
      a Children with data missing at the clinic visit before tTGA seroconversion were excluded (N = 14).
      b Reported gluten intake before age of tTGA seroconversion in children.
      Figure thumbnail gr1
      Figure 1Time to tTGA positivity by gluten intake (g) at the visit closest before tTGA seroconversion. Gluten intake was categorized by tertiles of quantity (ie, low [<3.4 g/d], medium [3.4–5.0 g/d], and high [>5.0 g/d]).

       Gluten Intake in Cases According to HLA Genotype

      Gluten intake at the visit before seroconversion of tTGA was not different among cases homozygous for DR3-DQ2 (median, 4.8 g; quartile 1 (Q1), 3.2; Q3, 5.9), heterozygous for DR3-DQ2 (median, 5.1 g; Q1, 3.8; Q4, 6.3), or in those without DR3-DQ2 (median, 4.9 g; Q1, 3.5; Q3, 5.9) (P = .49). To examine whether the association between increased gluten intake and CD risk differed by genetic susceptibility to CD, we examined this association separately in case-control pairs that were homozygous for the matching variable DR3-DQ2, pairs that were heterozygous for DR3-DQ2, and pairs without DR3-DQ2. In DR3-DQ2 homozygotes, children who received gluten in the upper tertile (high gluten intake) had a 3-fold higher risk for celiac disease than those who received less (OR, 3.19; 95% CI, 1.61–6.30; P = .001). A similar association was seen in DR3-DQ2 heterozygotes (OR, 2.24; 95% CI, 1.08–4.62; P = .030) and in children negative for DR3-DQ2 (OR, 2.43; 95% CI, 0.90–6.54; P = .079), albeit the latter did not reach statistical significance.

      Discussion

      In this nested case-control study, we showed that a high overall intake of gluten during the first 2 years of life, and in particular at 12 months of age, was associated with an increased risk for CD during childhood. More importantly, this association did not differ between children at very high or increased genetic risk for the disease; a high quantity of gluten still was associated with CD in children with no, 1, or 2 copies of the major celiac disease risk HLA-DR3-DQ2 haplotype. These findings may contribute to a better understanding of why some, but not all, children at genetic risk develop CD.
      Gluten-derived peptides are able to induce immune responses in individuals with DR3-DQ2 as well as with DR4-DQ8.
      • Arentz-Hansen H.
      • McAdam S.N.
      • Molberg Ö.
      • et al.
      Celiac lesion T cells recognize epitopes that cluster in regions of gliadines rich in proline residues.
      The disease risk is modified further by genotype, DR3-DQ2 homozygous individuals develop CD at an early age.
      • Mearin M.L.
      • Biemond I.
      • Peña A.S.
      • et al.
      HLA-DR phenotypes in Spanish coeliac children: their contribution to the understanding of the genetics of the disease.
      It has been hypothesized that the threshold of tolerance to gluten is dependent on the HLA genotype.
      • Tjon J.
      • van Bergen J.
      • Koning F.
      Celiac disease: how complicated can it get?.
      However, this proposed threshold model is supported only by in vitro studies showing that the strongest T-cell response is seen among DR3-DQ2 homozygous individuals who need only a small quantity of stimulatory gluten peptides to activate an immune response.
      • Vader W.
      • Stepniak D.
      • Kooy Y.
      • et al.
      The HLA-DQ2 gene dose effect in celiac disease is directly related to the magnitude and breadth of gluten-specific T cell responses.
      In this study, time to seroconversion of tTGA occurred a median of 12 months earlier among the high-risk group (DR3-DQ2 homozygous) than among the remaining cases with standard risk. It thus is tempting to speculate that the gluten intake needed for triggering CD was dependent on HLA risk genotype in this study. However, we found no indication that the gluten intake according to tertile distribution differed among cases carrying different HLA risk genotypes, indicating that the amount was an independent risk factor for CD to develop.
      Only 2 important studies have reported on the amount of gluten intake and subsequent risk for CD. In the European PreventCD study, the mean daily intake (after dose escalation) was not associated with an increased risk for CD.
      • Vriezinga S.M.
      • Auricchio R.
      • Bravi E.
      • et al.
      Randomized feeding intervention in infants at high risk for celiac disease.
      In contrast, another study indicated that the risk of CD was increased in Swedish children before 2 years of age who were introduced to gluten in large amounts during weaning.
      • Ivarsson A.
      • Hernell O.
      • Stenlund H.
      • et al.
      Breast-feeding protects against celiac disease.
      Swedish feeding practices differ from other European countries and the United States, which also was confirmed in the TEDDY cohort.
      • Andrén Aronsson C.
      • Uusitalo U.
      • Vehik K.
      • et al.
      Age at first introduction to complementary foods is associated with sociodemographic factors in children with increased genetic risk of developing type 1 diabetes.
      It is traditional to feed infants with cereal-based foods in Sweden. Moreover, Swedish infants are first introduced to gluten-containing foods at an earlier age and in larger amounts compared with other Nordic countries.
      • Aronsson C.A.
      • Lee H.
      • Liu E.
      • et al.
      Age at gluten introduction and risk for celiac disease.
      • Weile B.
      • Cavell B.
      • Nivenius K.
      • et al.
      Striking differences in the incidence of childhood celiac disease between Denmark and Sweden: a plausible explanation.
      • Ascher H.
      • Holm K.
      • Kristiansson B.
      • et al.
      Different features of coeliac disease in two neighbouring countries.
      By tradition, most common cereal-based foods given to Swedish infants are cereal in milk formulations (gruel) or spoon-fed porridges, which are nutritionally similar products. At the age of 6 months, 60% of Swedish children were bottle-fed with 250 to 500 mL of gruel per day and almost all infants were given porridge.
      • Almquist-Tangen G.
      • Dahlgren J.
      • Rosvall J.
      • et al.
      Milk cereal drink increases BMI risk at 12 and 18 months, but formula does not.
      The major source of gluten in gluten-containing commercial baby foods comes from wheat and rye flour. In Sweden, gruels and porridges are available in numerous brands and for different age groups. The gluten-content in these types of products is between 0.3 and 0.7 g gluten per 100 g of prepared product (data based on the recipes created in the Swedish nutrient database). In our study, we showed a sharp increase in the reported amount of gluten between 9 and 12 months of age. This is typically the time when many infants are given gluten-containing commercial feeding products in Sweden. This could suggest that porridges and gruel given in large amounts modulate the risk of CD during early childhood in Sweden after controlling for HLA risk genotype.
      • Liu E.
      • Lee H.
      • Aronsson C.A.
      • et al.
      HLA Haplotype and country and the risk of celiac disease in early childhood.
      The strength of the present study was the prospective design with the use of a 3-day food record for the dietary assessment of early childhood food consumption. This method provides a more accurate estimation about gluten intake compared with dietary assessment methods using standard portions such as food frequency questionnaires. During the first year of life, parents kept a food record frequently and with a very high compliance rate. The face-to-face visits made it possible to probe about missing portion sizes, which maximized the efforts of collecting complete data. The prospective design of this birth cohort study enabled us to obtain the diet information before seroconversion of tTGA as a marker of CD. This eliminated the risk of reporting biases or a change in feeding habits because of the knowledge of serology results or disease status. A potential weakness of the study was that we did not analyze information about the number of servings of gluten-containing foods per day. We cannot exclude the possibility, for example, that the number of portions given frequently during the course of the day may have different effects on disease risk.
      In conclusion, this study showed that a high intake of gluten during the first 2 years of life is associated with an increased risk of CD. This association was similar in children carrying any of the major HLA risk genotypes for CD. Because these HLA risk genotypes also are widely distributed in the general population, our findings therefore may have consequence for future infant feeding recommendations. Future studies from other countries are warranted to confirm if gluten intake during infancy triggers celiac disease in young children.

      Acknowledgments

      The authors express their gratitude to the families who participated in the study. Members of the TEDDY Study Group are listed in the Supplementary Appendix.

      Supplementary Appendix 1

       The Teddy Study Group

      The following were members of the Colorado Clinical Center: Marian Rewers, MD, PhD, Principal Investigator,1,4–6,10,11 Kimberly Bautista,12 Judith Baxter,9,10,12,15 Ruth Bedoy,2 Daniel Felipe-Morales, Brigitte I. Frohnert, MD,14 Patricia Gesualdo,2,6,12,14,15 Michelle Hoffman,12–14 Rachel Karban,12 Edwin Liu, MD, PhD,13 Jill Norris, PhD,2,3,12 Adela Samper-Imaz, Andrea Steck, MD,3,14 Kathleen Waugh,6,7,12,15 and Hali Wright12 (University of Colorado, Anschutz Medical Campus, Barbara Davis Center for Childhood Diabetes).
      The following were members of the Georgia/Florida Clinical Center: Jin-Xiong She, PhD, Principal Investigator,1,3,4,11 Desmond Schatz, MD, PhD (University of Florida),4,5,7,8 Diane Hopkins,12 Leigh Steed,12–15 Jamie Thomas (University of Florida),6,12 Janey Adams (University of Florida),12 Katherine Silvis,2 Michael Haller, MD, PhD (University of Florida),14 Melissa Gardiner, Richard McIndoe, PhD, Ashok Sharma, Joshua Williams, Gabriela Foghis, Stephen W. Anderson, MD (Pediatric Endocrine Associates, Atlanta), and Richard Robinson (Center for Biotechnology and Genomic Medicine, Georgia Regents University).
      The following were members of the Germany Clinical Center: Anette G. Ziegler, MD, PhD, Principal Investigator,1,3,4,11 Andreas Beyerlein, PhD,2 Ezio Bonifacio, PhD (Center for Regenerative Therapies, TU Dresden),5 Michael Hummel, MD, PhD,13 Sandra Hummel, PhD,2 Kristina Foterek (Research Institute for Child Nutrition, Dortmund),2 Mathilde Kersting, PhD (Research Institute for Child Nutrition, Dortmund),2 Annette Knopff,7 Sibylle Koletzko, MD, PhD (Dr. von Hauner Children’s Hospital, Department of Gastroenterology, Ludwig Maximillians University Munich),13 Claudia Peplow,12 Roswith Roth, PhD,9 Joanna Stock,9,12 Elisabeth Strauss,12 Katharina Warncke, MD,14 and Christiane Winkler, PhD2,12,15 (Forschergruppe Diabetes e.V. and Institute of Diabetes Research, Helmholtz Zentrum München, and Klinikum rechts der Isar, Technische Universität München).
      The following were members of the Finland Clinical Center: Jorma Toppari, MD, PhD, Principal Investigator (University of Turku, Turku University Hospital, Hospital District of Southwest Finland),1,4,11,14 Olli G. Simell, MD, PhD (University of Turku, Turku University Hospital, Hospital District of Southwest Finland),1,4,11,13 Annika Adamsson, PhD (Turku University Hospital, Hospital District of Southwest Finland),12 Heikki Hyöty, MD, PhD (University of Tampere, Tampere University Hospital),6 Jorma Ilonen, MD, PhD (University of Turku, University of Kuopio),3 Sanna Jokipuu (Turku University Hospital, Hospital District of Southwest Finland), Tiina Kallio (Turku University Hospital, Hospital District of Southwest Finland), Miia Kähönen (University of Oulu, Oulu University Hospital), Mikael Knip, MD, PhD (University of Tampere, Tampere University Hospital),5 Annika Koivu (University of Turku, Turku University Hospital, Hospital District of Southwest Finland), Mirva Koreasalo (University of Tampere, Tampere University Hospital, National Institute for Health and Welfare, Finland),2 Kalle Kurppa, MD, PhD (University of Tampere, Tampere University Hospital),13 Maria Lönnrot, MD, PhD (University of Tampere, Tampere University Hospital),6 Elina Mäntymäki (University of Turku, Turku University Hospital, Hospital District of Southwest Finland), Katja Multasuo (University of Oulu, Oulu University Hospital), Juha Mykkänen, PhD (University of Turku, Turku University Hospital, Hospital District of Southwest Finland),3 Tiina Niininen (University of Tampere, Tampere University Hospital),12 Mia Nyblom (University of Tampere, Tampere University Hospital), Petra Rajala (Turku University Hospital, Hospital District of Southwest Finland), Jenna Rautanen (Tampere University Hospital, National Institute for Health and Welfare, Finland), Anne Riikonen (University of Tampere, Tampere University Hospital), Minna Romo (University of Turku, Turku University Hospital, Hospital District of Southwest Finland), Satu Simell, MD, PhD (Turku University Hospital, Hospital District of Southwest Finland, Tampere University Hospital),13 Tuula Simell, PhD (University of Turku, Turku University Hospital, Hospital District of Southwest Finland), Ville Simell (University of Turku, Turku University Hospital, Hospital District of Southwest Finland),13 Maija Sjöberg (University of Turku, Turku University Hospital, Hospital District of Southwest Finland),12,14 Aino Stenius (University of Oulu, Oulu University Hospital),12 Maria Särmä (Turku University Hospital, Hospital District of Southwest Finland), Sini Vainionpää (Turku University Hospital, Hospital District of Southwest Finland), Eeva Varjonen (University of Turku, Turku University Hospital, Hospital District of Southwest Finland),12 Riitta Veijola, MD, PhD (University of Oulu, Oulu University Hospital),14 Suvi M. Virtanen, MD, PhD (University of Tampere, Tampere University Hospital, National Institute for Health and Welfare, Finland),2 Mari Vähä-Mäkilä (Turku University Hospital, Hospital District of Southwest Finland), and Mari Åkerlund (University of Tampere, Tampere University Hospital, National Institute for Health and Welfare, Finland).
      The following were members of the Sweden Clinical Center: Åke Lernmark, PhD, Principal Investigator,1,3–6,8,10,11,15 Daniel Agardh, MD, PhD,13 Carin Andrén Aronsson,2,13 Maria Ask, Jenny Bremer, Ulla-Marie Carlsson, Corrado Cilio, PhD, MD,5 Emelie Ericson-Hallström, Lina Fransson, Thomas Gard, Joanna Gerardsson, Rasmus Bennet, Monica Hansen, Gertie Hansson,12 Cecilia Harmby, Susanne Hyberg, Fredrik Johansen, Berglind Jonasdottir, MD, Helena Elding Larsson, MD, PhD,6,14 Sigrid Lenrick Forss, Markus Lundgren, MD,14 Maria Månsson-Martinez, Maria Markan, Jessica Melin,12 Zeliha Mestan, Kobra Rahmati, Anita Ramelius, Anna Rosenquist, Falastin Salami, Sara Sibthorpe, Birgitta Sjöberg, Ulrica Swartling, PhD,9,12 Evelyn Tekum Amboh, Erika Trulsson, Carina Törn, PhD,3,15 Anne Wallin, Åsa Wimar,12,14 and Sofie Åberg (Lund University).
      The following were members of the Washington Clinical Center: William A. Hagopian, MD, PhD, Principal Investigator,1,3–7,11,13,14 Michael Killian,6,7,12,13 Claire Cowen Crouch,12,14,15 Jennifer Skidmore,2 Stephen Ayres, Kayleen Dunson, Rachel Hervey, Corbin Johnson, Rachel Lyons, Arlene Meyer, Denise Mulenga, Elizabeth Scott, Joshua Stabbert, Alexander Tarr, Morgan Uland, and John Willis (Pacific Northwest Diabetes Research Institute).
      The following were members of the Pennsylvania Satellite Center: Dorothy Becker, MD, Margaret Franciscus, MaryEllen Dalmagro-Elias Smith,2 Ashi Daftary, MD, Mary Beth Klein, and Chrystal Yates (Children’s Hospital of Pittsburgh of University of Pittsburgh Medical Center).
      The following were members of the Data Coordinating Center: Jeffrey P. Krischer, PhD, Principal Investigator,1,4,5,10,11 Michael Abbondondolo, Sarah Austin-Gonzalez, Sandra Baethke, Rasheedah Brown,12,15 Brant Burkhardt, PhD,5,6 Martha Butterworth,2 Joanna Clasen, David Cuthbertson, Christopher Eberhard, Steven Fiske,9 Dena Garcia, Jennifer Garmeson, Veena Gowda, Kathleen Heyman, Francisco Perez Laras, Hye-Seung Lee, PhD,1,2,13,15 Shu Liu, Xiang Liu, PhD,2,3,9,14 Kristian Lynch, PhD,5,6,9,15 Jamie Malloy, Cristina McCarthy,12,15 Wendy McLeod, Steven Meulemans, Chris Shaffer, Laura Smith, PhD,9,12 Susan Smith,12,15 Noah Sulman, PhD, Roy Tamura, PhD,1,2,13 Ulla Uusitalo, PhD,2,15 Kendra Vehik, PhD,4–6,14,15 Ponni Vijayakandipan, Keith Wood, and Jimin Yang, PhD, RD2,15; and past staff included Lori Ballard and David Hadley, PhD (University of South Florida).
      The project scientist was Beena Akolkar, PhD1,3–7,10,11 (National Institutes of Diabetes and Digestive and Kidney Diseases).
      The following were other contributors: Kasia Bourcier, PhD5 (National Institutes of Allergy and Infectious Diseases), Thomas Briese, PhD6,15 (Columbia University), Suzanne Bennett Johnson, PhD9,12 (Florida State University) and Eric Triplett, PhD6 (University of Florida).
      The committees were as follows: 1Ancillary Studies, 2Diet, 3Genetics, 4Human Subjects/Publicity/Publications, 5Immune Markers, 6Infectious Agents, 7Laboratory Implementation, 8Maternal Studies, 9Psychosocial, 10Quality Assurance, 11Steering, 12Study Coordinators, 13Celiac Disease, 14Clinical Implementation, and 15Quality Assurance Subcommittee on Data Quality.
      Figure thumbnail fx1
      Supplementary Figure 1Flow chart of study enrollment and participation in the Swedish TEDDY birth cohort.

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